High pressure gear pump



Sept. 19, 1961 s. RK ET AL 3,000,323

HIGH PRESSURE GEAR PUMP Filed April 14, 1960 2 Sheets-Sheet 1 ATTORNFFS.

Sept. 19, 1961 G. s. PARK ETAL 3,000,323

HIGH PRESSURE GEAR PUMP Filed April 14, 1960 2 Sheets-Sheet 2 1 E ORE fi f United, States, PatentO 3,000,323 HIGH PRESSURE GEAR PUMP Glenn S. Park, New Berlin, and George A. Rea, Wauwatosa, Wis., assignors to TheHeil C0., Milwaukee, Wis., a corporation of Wisconsin Filed Apr. 14, 1960, Ser. No. 22,229

8 Claims. (Cl. 103-126) V r This invention relates to improvements in high pressure gear pumps. 7 Pressure loaded gear pumps are traditionally pumps in which one (or one set of) wear plates has pump output pressure fed to the cover side of the wear plate. This area which is exposed to full pump pressure on the cover side of the. wear plate must be large enough so the pump pressure times this area is greater than the force on the gear side of the wear plate caused by the internal pump pressures on the efiective area of the gear side of the wear plate. If it were less, then the pump would unload due to the wear plate moving away from the gear under pressure. One problem with a design such as this is that the pressure on the gear side of the wear plate varies from full. output pressure on the pressure side down to pump inlet pressure on the suction side. This produces a tendency to cock or tip the wear plate around a vertical axis through the gears away from the pump on the pressure side. In turn the pressure loading on the cover side of the wear plate will produce very high bearing pressures of the wear plate on the gear on the suction side down to very low or no bearing pressure of the wear-plate on the gear on the pressure side. The net result is that if this cocking or tipping moment is not compensated for by some means, still more loading pressure is required, with resulting higher bearing pressures on the suction side of the wear plate, which is undesirable.

It is a general object of the present invention to provide novel and effective means for compensating for the tipping moment in a high pressure gear pump, said means materially reducing the amount of pressure loading required.

7 A more specific object of the invention is to provide a construction as above described wherein the tipping moment is compensated for by a combination of what may be termed a pull piston, which in effect merely subtracts a portion of the area on the suction side of the cover side of the wear plate subject to pressure, and a push piston which pushes on the pressure side of the wear plate. The push piston utilizes full pump output pressure.

The'pressure gradient from high to low within a pump of this type is variable even at a given output prmsure and is dependent upon several factors. This variable gradient results in a variable unloading force. If the pressure loading in a pump of this type is a direct function of only the pump output pressure, then under certain operating conditions the loading force can become excessive, causing heat and rapid wear on the wear plates and gear ends.

It'is, therefore, a further object of this invention to compensate for this variable unloading force and provide a variable loading force through the selection of ,a pressure pick-up point within the pressure gradient that lies between the high=and low pressure sides, the present invention providing a self compensating effect, that is, rather than utilizing full pump output pressure on the cover side of the wear plate, a reduced pressure is used by taking the oil for the pressure loading at a gradient point which is located somewhere other than at full'pump pressure. a I With the above and other objects in View, the inven- 2* tion consists of the improved high pressure gear pump, and all of its parts and combinations, as set forth in the claims, and all equivalents thereof.

In the accompanying drawings, illustrating one complete embodiment of the preferred form of the invention, in which the same reference numerals designate the same parts in all of the views:

FIG. 1 is an end view of the improved pump;

FIG. 2 is a sectional view taken approximately on the line 2-2 of FIG. 1;-

FIG. 3 is a view of the opposite end from that shown in FIG. 1;

FIG. 4 is a horizontal sectional view taken on line 4-4 of FIG. 3; and p FIG. 5 is a plan view of the one piece wear plate looking at the gear side thereof with one location of the loading ports shown in full lines and with alternative loading port positions indicated by dot and dash lines;

Referring more particularly to the drawings, the numeral 8 designates a pump housing having an inlet or low pressure passageway 9 and an outlet or high pressure passageway 10, and the numeral 11 a cover plate. Suitably journaled in the housing and cover plate to plOf ject from the cover plate are shafts 12' and 13. The shaft 12 has a gear 14 rigidly mounted thereon for-rotation therewith and the shaft 13 has a gear 15 rigidly mounted thereon for rotation therewith, said gears-fo tating with the pump chamber 16 and being in mesh with one another to pump liquid entering the suction passageway 9 =and to expel it under pressure through the outlet or high pressure'passageway 10.

The ends of the gears which are remote from the cover rotate against a thrust plate or plates 17. The oppo'e site ends of the gears are in contact with a one piece steel wear plate 18 having an aluminum alloy facing 191 The wear plate also has external grooves 20 forms.- ceiving O-rings 2.1 to seal the wear plate around the bearings. In addition the housing has a surrounding groove 22 for receiving an O-ring 23 which seals against the outer periphery of the wear plate. Small springs 24, seated in recesses 25 of the cover, bear against the wear plate as shown in FIG. 2. These springs serve to push the wear plate up against the gears for low pressure operation and serve to overcome O-ring friction.

Referring now to FIG. 4 the pump housing has a duct 26 leading from the high pressure passageway and registering with a duct 27 in the cover. The duct 27 in turn communicates with a branch cover duct 28. The outer end of the duct 28 is accessible from the exterior when a plug 29 is removed. The inner end of the duct 28 communicates with a cylindrical chamber 30, within which a push piston 31 is movable, the latter being surrounded by an O-ring 30' in an annular groove in the cover. The push piston engages a pin 32 which bears against the wear plate 18, and which is mounted for sliding move' ment in a bore 33, there being an O-ring 34 seal around the pin 32. This push piston is influenced by full pump output presure to exert a push on the portion of the wear plate contacted by the stem. 32. V p

On the low pressure side of the pump the main casing has a duct 35 in registry with a duct 36 in the cover The latter communicates with .a branch duct 37. The duct 37 has an outer end which is normally closed by a plug 38, and an intermediate portion of the duct 37 communicates with a cylindrical chamber 39 for a pull .piston 40. A bolt 41 projecting from the pull piston 40 is tapped into the wear plate 18 as at 42 and there is a spring 43 surrounding the bolt between the wear plate and the piston 40 normally urging the piston outwardly. An O-ring 44, in an annular groove of the cover, seals against the exterior periphery of the pisten 40.

v The duct 37 has its inner end communicating through ducts 45 and 46 with the chamber 39 for the piston 31 beneath the piston. This drains off any leakage from seals 34 or 30 back to the suction side and thereby prevents build-up of pressure behind the piston 31.

The pressure loading ports, which allow liquid under pressure from the chamber 16 to travel to the cover side of the wear plate 18 to push it toward the gears 14 and 15 are designated by the numerals 47 and 48 in FIG. 2. These are specially located as will be hereinafter described.

Operation As a result of this arrangement pressure from the pressure side of the pump acts through the ducts 26, 27 and 28 to push on the piston 31 and hence act onthe portion of the wear plate 18 which is contacted by the pin 32. At the same time, however, wear plate loading pressure acts on the inner side of piston 40 to exert an outward push on the piston 40, and hence piston 4i) exerts a pull on the portion of the wear plate 18 to which the bolt 41 is connected. This pull piston serves to subtract :1 portion of the area of the cover side of the wear plate adjacent'the suction side of the pump, whereas the push piston 31 pushes on the cover side of the wear plate adjacent the pressure side of the pump. Thus an anti-cock! ing couple is produced. With this arrangement the amount of pressure loading necessary on the cover side of the wear plate can be materially reduced since none of the cocking couple needs to be overcome by the pressure loading means. The pressure loading force originating from the ports 47 and 48 and which moves the wear plate into contact with the ends of the gears must be greater than the opposing torce caused by the pressure within the main chamber 16 of the pump acting on the gear side of the wear plates. This pressure gradient from the high pressure side to the low pressure side within the pump chamber is variable even at a given output pressure. This variable gradient depends upon several factors other than output pressure, such as tolerances, oil viscosity and operating speed. This variable gradient results in a variable unloading force. If the pressure loading force acting on the cover side of the wear plate is a direct function of the pump output pressure only, then under certain operating conditions, the loading force can become excessive causing heat and rapid wear on the wear plates and gear ends. With the present invention this is overcome by locating the ports 47 and 48 somewhere other than at full pump pressure. In the embodiment of the invention illustrated they are located on the vertical center lines of the gears. The precise location of the pressure loading ports 47 and 4S depends upon the geometry of the'pumpq To explain further, the gradient points may be arbitrarily selected by tests to be at points equal to 60% of pump output pressure. This 60% figure is dependent upon several factors such as pump output pressure, speed, oil viscosity, pump wear, etc. However, if under certain conditions the 60% figure became 75% the net effective pressure loading would remain fairly constant since although the load on the cover side of the wear plate is increased, so also is the load on the gear side of the wear plate. This in efiect makes the design self compensating for a change in pressure loading pressure,

In the embodiment of the invention which has been illustrated, the loading ports 47 and 48 are shown as located on the vertical center line of the gears. It is possilbe to vary this location as much as 90 on either side of the ports 47 and 48 shown by, full lines in FIG. 5. Very good results, however, are obtained in certain pump designs by having the ports located as shown at 47' and 48', approximately 30 over toward the low pressure side of the pump.- If less loading pressure is desired, the ports are moved farther over toward the low pressure side, whereas, if more loading pressure is desired the ports can be moved toward the high pressure side as at 47 and 48", FIG. 5.

It is to be understood that the present invention is not to be limited to the exact details of construction shown and described for obvious modifications will occur to persons skilled in the art;

What we claim is:

1. In a high pressure gear pump of the type including a housing having intermeshing gears and having a low pressure inlet leading to and a high pressure outlet leading from said housing, a single axially movably mounted wear plate in said housing in contact with end faces of both of said gears, there being means including pressure pick-up ports through said wear plate from the gear side to the back side for pressure loading the back face of said wear plate to urge it into contact with said gear end faces, anti-cocking means in communication with and responsive to pressure from said high pressure outlet and independent of said loading pressure for pushing a pore tion of said wear plate at said high pressure side of the pump inwardly toward the gears, anti-cocking means in communication with and responsive to pressures from said pressure loading means urging the portion of the wear plate at the low pressure side of the pump outwardly away from the gears, said anti-cocking means compensating for normal cocking tendencies of said Wear plate.

2. In a high pressure gear pump of the type includa housing having intermeshing gears and having a low pressure inlet leading to and a high pressure outlet lead-. ing froinsaid housing, a single axially movably mounted wear plate in said housing in contact with end faces of both of said gears, there being means including pressure pickup ports in said wear plate for loading the back face of said wear plate to urge it toward and into contact with said gear end faces, anti-cocking means in communication with and responsive to pressure from said high pressure outlet and independent of said loading pressure for pushing a portion of said wear plate at said high pressure side of the pump inwardly toward the gears, anticocking means in communication with and responsive to pressures from said pressure loading means urging the portion of the wear plate at the low pressure side of the pump outwardly away from the gears, said two anti-cocking means compensating for normal cocking tendencies of said wear plate, said pressure pickup ports in the wear plate being located remotely from said high pressure outlet and intermediate the pump inlet and outlet pressures so that pressure loading is at a pressure substantially less than full pump pressure to compensate for changes in pressure loading pressures.

3. In a high pressure gear pump of the type including a housing having a main pump chamber with intermeshing gears and having a pressure loading chamber, and having a low pressure inlet leading to and a high pressure outlet leading from said main pump chamber, a single axially movably mounted wear plate in said housing in front of said loading chamber and in contact with the end faces of both of said gears, there being means for by-passing fluid under pressure from said main chamber to said loading chamber to load the .back face of said wear plate and urge it against said gear end faces, there also being a first cylinder in said housing, a push piston slidable in said cylinder, there being communication between said first cylinder and the high pressure outlet from the pump so located as to push said push piston toward the wear plate, means between said piston and a portion of said wear plate at said high pressure side of the pump for exerting an inward force toward the gears on said portion of the wear plate in response to pressure from the push piston, there also being a second cylinder in said housing having an inner end and an outer end, a pull piston slidably mounted in said second cylinder, the

"sbodsis portion of the wear plate on the low pressure side of the pump for pulling said wear plate portion outwardly away from the gears when said pull piston is moved outwardly by loading pressures, said two pistons providing an anticocking couple for the wear plate.

4. In a high pressure gear pump of the type including a housing having a main pump chamber with intermeshing gears and having a pressure loading chamber and having a low press'ure'inlet leading to and a high pressure outlet leading from said main pump chamber, a single axially movably mounted 'wear plate in said housing in contact with the end faces of both of said gears, pressure pick-up ports in said wear plate for by-passing fluid under pressure from'said main chamber to said loading chamber to load the back face of said wear plate and urge it against said gear end faces, there also being a first cylinder in said housing, a push piston slidable in said first cylinder, there being communication between said first cylinder and the high pressure outlet from the pump so located as to push said push piston toward the wear plate, means between said push piston and a portion of said wear plate near said high pressure side of the pump for exerting an inward force toward the gears on said portion of the wear plate at the high pressure side of the pump in response to pressure from the push piston, there also being a second cylinder in said housing having an inner end and an outer end, a pull piston slidably mounted in said second cylinder, the outer end of said second cylinder being in communication with the low pressure side of said pump and the inner end of said second cylinder being in communication with said pressure loading chamber whereby the pull piston is urged outwardly by loading pressures, and a connection between said last piston and the portion of the wear plate on the low pressure side of the pump for pulling said portion outwardly when said pull piston is moved outwardly by loading pressures, said two pistons providing an anti-cocking couple for the wear plate to compensate for normal cocking tendencies, said pressure pick-up ports in the wear plate being located remotely from said high pressure outlet and intermediate the pump inlet and outlet pressures so that pressure loading is at a pressure substantially less than full pump pressure to compensate for changes in pressure loading pressures.

5. In a high pressure gear pump of the type including a housing with a cover, said housing having a main pump chamber with intermeshing gears and having a pressure loading chamber and having a low pressure inlet leading to and a high pressure outlet leading from said main pump chamber, a single axially movably mounted wear plate in said housing in contact with the end faces of both of said gears, there being means for by-passing fluid under pressure from said main chamber to said loading chamber to load the back face of said wear plate and urge it against said gear end faces, there also being a first cylinder in said cover, a push piston slidable in said first cylinder, there being communication between said first cylinder and the high pressure outlet from the pump so located as to push said push piston toward the wear plate, means between said piston and a portion of said wear plate at said high pressure ide of the pump for exerting an inward force toward the gears on said portion of the wear plate in response to pressure from the push piston, there also being a second cylinder in said cover having an inner end and an outer end, a pull piston slidably mounted in said second cylinder, the outer end of said second cylinder being in communication with the low pressure side of said pump and the inner end of said second cylinder being in communication with said pressure loading chamber whereby piston'is urged outwardly "away by loading pressures, and a connection between said last piston and the portion of the wear plate at thelow pressure side of the pump for pulling said portion outwardly away from the gears when said pull piston is moved outwardly by loading pressures, said two pistons providing an anti-cocking couple for the wear plate to compensate for normal cocking tendencies.

6. In a high pressure gear pump of the type including a housing having a main pump chamber with intermeshiug gears and having a pressure loading chamber,

and having a low pressure inlet leading to and a high pressure outlet leading from said main pump chamber, a single axially movably mounted wear plate in said housing in front of said loading chamber and in con tact with the end faces of both of said gears, there being means for by-passing fluid under pressure from said main chamber to said loading chamber to load the back face of said wear plate and urge it against said gear end faces, there also being a first cylinder in said housing,

means including a push piston slidable in said first cylinider responsive to fluid pressure from the high pressure "outlet of the pump for exerting an inward force toward the gears on the portion of the wear plate at the high pressure side of the pump, there also being a second cylinder in said housing having an inner end and an outer end, a pull piston slidably mounted in said second cylinder, the outer end of said second cylinder being in communication with the low pressure inlet of said pump and the inner end of said second cylinder being in communication with said pressure loading chamber whereby the pull piston is urged outwardly away from the gears by loading pressures, and a connection between said last piston and the portion of the wear plate at the low pressure side of the pump for pulling said wear plate portion outwardly away from the gears when said pull piston is moved outwardly by loading pressures, said two pistons providing an anti-cocking couple for the wear plate. 7. In a high pressure gear pump of the type including a housing having a main pump chamber with intermeshing gears and having a pressure loading chamber and having a low pressure inlet leading to and a high pressure outlet leading from said main pump chamber, a single axially movably mounted wear plate in said housing in contact with the end faces of both of said gears, pressure pick-up ports in said wear plate for by-passing fluid under pressure from said main chamber to said loading chamber to load the back face of said wear plate and urge it against said gear end faces, there also being a first cylinder in said housing, a push piston slidable in said first cylinder, there being communication between said first cylinder and the high pressure outlet from the pump so located as to push said push piston toward the wear plate, means between said push piston and a portion of said wear plate near said high pressure side of the pump for exerting an inward force toward the gears on said portion of the wear plate at the high pressure side of the pump in response to pressure from the push piston, there also being a second cylinder in said housing having an inner end and an outer end, a pull piston slidably mounted in said second cylinder, and the inner end of said second cylinder being in communication with said pressure loading chamber whereby the pull piston is urged outwardly by loading pressures, and a connection between said last piston and the portion of the wear plate on the low pressure side of the pump for pulling said portion outwardly when said pull piston is moved outwardly by loading pressures, said two pistons providing an anti-cocking couple for the wear plate to compensate for normal cocking tendencies, said pressure pickup ports in the wear plate being located remotely from said high pressure outlet and intermediate the pump inlet and outlet pressures so that pressure loading is at a pressure substantially less than full pump pressure to compensate for changes in pressure loading pressures.

in; ge r an having a p ssure loading chamber an having a l pr n t l a ing o and'a high pr ssur outle l ding from s id main pump chamber, a single .agtially movably mounted Wear plate in said housing in contact with the end faces of both of said gears, Pressure pick-up ports in said wear plate for bypassing fluid un r p s r ir m said. main ch mber to. s i l di chamber to load the back face of said wear plate, and

urg it g in said gear end tapes, there also being a first cylinder in said housing, a push piston slidable in said first cylinder, there being communication between 'said first cylinder and the high pressure outlet from the pump so located as to push said push piston toward the we r pl e, m n w n s id push pis n. and a p rtion of said Wear plate near said high pressure side of the pump for exerting an inward force toward the gears on said portion f. the wearpl t a he igh p es ure side of the pump in response to pressure from the p sh piston, there also being a seeond eylindet in .SAaid housing ha i g an u ei end and an outer en a 11% piston li mounted in said second cylinder, and the inner end of said second cylind r being in eomnuu ieeti n with Said pressure loading lqha mber whereby the pull piston i rged outwardly by l ading pre s res, and a connection between said last piston and, the portion of the wear plate on the low pressure side of the pump for pulling said portion outwardly when said pull piston is move outwardly by loading pressure sai tw pistons providing an anti-cooking couple for the wear plate to compensate for normal cocking tendencies.

References Cited in the tile of this patent UNITED STATES PATENTS 2,044,873 Beust .7. June 23, 1936 2,728,301 Lindberg ,i i Dec. 27, 1955 2,809,592 Miller et a1. Oct. 15, 1957 2,816,510 Jarvis Dec. 17, 1957 2,842,066 Hilton July 8, 1958 2,923,248 Hodgson Feb. 2, 1960 2,932,254 Booth et a1. Apr. 12, 1960 FOREIGN PATENTS 1.121.180 France "em-a endas, Apr- 30, 195 

